Components and Characteristics of the Instrument Landing System (ILS)
T-45A UJPT & E2-C2 INav-04
d.
Standard ILS glideslope is 2.5 to 3.0 degrees (may be higher
or lower depending on local terrain)
e.
Glideslope utilizes two signal lobes projected one above the
other. Upper lobe is modulated with 90 Hz and the lower lobe
at 150 Hz at an equal signal strength
f.
Each lobe is approximately 0.7 degrees wide with a total beam
width of approximately 1.4 degrees wide
g.
The point of equal signal modulation sets the center of the
glideslope beam
NOTE: The signal provides descent information for navigation
down to the lowest authorized decision height (DH) specified in
the approved ILS approach procedure. The glidepath may not
be suitable for navigation below the lowest authorized DH and
any reference to glidepath indications below that height must
be supplemented by visual reference to the runway
environment.
NOTE: Glidepaths with no published DH are usable to runway
threshold. Pilots of T-45A aircraft will execute a missed
approach at the MM or 200 ft AGL whichever occurs first.
NOTE: ILS installations that share the same frequency can
exist at each end of a given runway or at other runways on an
airport but cannot be in operation at the same time. However,
fields can have ILS approaches to different runways that do not
share the same frequency and can operate simultaneously.
5.
The glideslope transmitter operates on one of 40 dedicated ILS
channels
a.
Generates within the UHF frequency range of 329.15 and
335.00 MHz.
b.
Dedicated glideslope UHF frequencies are paired with
dedicated localizer VHF frequencies and are automatically
tuned upon selection of a localizer frequency
CAUTION: Pilots should be aware that false glide-
slope signals may exist. This can cause the glideslope
warning flag to disappear and a glideslope indication
to appear on your navigation instruments. Always
disregard any glideslope indication when the aircraft
is not on a published portion of an ILS approach at a
published approach altitude where the glideslope
interception is indicated and anticipated.
Page 4-8
(6-99) Original
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